Depends on what you sell. I had one once, and it did okay.
The trick is to have a huge inventory of reasonably-priced items with a cheap rate on combined shipping and run lots and lots of related auctions to draw attention to the store items.
If you price the items in your store for around what they typically end for in auctions, and you have a ton, and your items are related to what you sell at auctions, you should do well.
eBay Store is a good concept, but having a store needs to be free. eBay gets their money from final value fees and listing fees anyway. It doesn't cost them anything for you to have a store. I think there would be a lot more stores with a lot bigger inventories if eBay would stop charging for them.
I don't have my store anymore because I wasn't making enough to cover the monthly store fee. And even if I were, that's basically me giving away my cards to keep the store open. But then, I didn't follow the advice I laid out above, so your mileage may vary.
